Abstract
Coarse and irregular precipitates of carbide along grain boundaries are now well known to increase creep rupture strengths of austenitic heat resisting steels, through the effect of retarding grain boundary cracking. In an 18Cr-12Ni-0.3C steel, for instance, the coarse carbide precipitation occurs when the steel is solution-treated at such a temperature that makes the carbide dissolve completely (the first step temperature), directly cooled to the second step temperature that is a little lower than the solvus temperature of the carbide, held at the second step temperature, if necessary, and water-quenched.
In the present paper, the effect of rolling deformation at the second step of the treatment mentioned above has been studied. The purpose of this thermo-mechanical treatment is two fold; it is intended first that the irregularity in grain boundaries may be increased by the formation of small recrystallized grains along the original grain boundary or by the bulging of a grain to another, and secondly that the proof stress may be increased by the work hardening without recrystallization. The first aim is not realized due to the occurence of unexpected types of recrystallization, while the second one is achieved.
